Each hour of exposure to wildfire smoke is equivalent to smoking cigarettes continuously for the same amount of time, according to one lung expert.
Smoke is billowing from hundreds of fires across California, Oregon and Washington, drifting cross country and reaching as far as eastern Canada and Europe.
While the smoke was not expected to impact air quality in any eastern states, it remained at dangerous levels in the west.
One of the most dangerous pollutants from wildfires is tiny particles which suspend in the air as the fires burn.
The particles are no larger than one third the diameter of a hair follicle, according to the American Lung Assocation, and can lodge deep in the lungs when breathed in.
"If you are exposed for 12 hours of smoke in the air, then that is like 12 hours of continued smoking,” Dr Zab Mosenifar, a critical care pulmonologist at Cedars Sinai Medical Center, told NBC.
Particle pollution triggers asthma attacks, heart attacks and strokes — and can be deadly. Studies of children in California found that those who breathed the smoky air during wildfires had more coughing, wheezing, bronchitis and colds.
They were also more likely to need medical care for respiratory causes, especially from asthma.
Here are some tips to protect yourself.
Seal your home from smoke
Priority number one should be keeping doors and windows shut if you’re living in an area where the air quality is at dangerous levels. If you have leaks, use weather sealing or masking tape along window gaps. A damp towel can also be placed at the base of a door to prevent smoke from seeping in.
The safest place within your home is where there are few doors, windows, and ventilation ducts connected to the outside. Remain in that room for the majority of the day if possible.
Use an air purifier
Air purifiers, which can be purchased online through most retailers, help filter the air within your home. Consider purchasing an air purifier to help improve your indoor air quality. Those properly fitted with HEPA filters can reduce particle concentrations by as much as 85 per cent, according to the EPA.
If an air purifier is not available for purchase then run your air conditioner in recirculation mode so it only circulates the air within your home instead of pulling from outdoors. Also, if using your air conditioner’s fan, make sure it is set to “on” instead of “auto”.
Avoid activities that increase indoor pollution
Vacuuming, frying food, using a gas stove, and smoking are all activities that can increase your indoor air pollution. Experts recommend limiting these activities as much as possible to keep the air within your home free of pollutants.
Clean your air filter
The filters within your air ducts should typically be switched out two to three times per year. But wildfire smoke can increase how often these filters should be cleaned. Check your filters daily to make sure they are still properly trapping debris from passing into your home.
Besides keeping filters clean, it is also important for you to have the right size filter to make sure it traps as many particles as possible. Health experts recommend using HEPA filters, as they use a fan to force air through fine mesh that will trap particles in indoor heating, ventilation, cooling and air purification systems.
Avoid outdoor activities
Exercising outdoors, mowing the lawn, or performing other outside activities will increase your exposure to unsafe conditions. The CDC and other health experts recommend limiting your exposure outdoors and avoiding strenuous activities like working out.
If you go outside, an N95 mask is one of the best to filter out particles, though these masks are not easily available due to the coronavirus pandemic. Masks made from multiple types of fabrics, such as cotton and silk woven together, can be another alternative for a face covering if N95s are not available.